The present invention relates to a device for transluminal extraction or implantation of a substantially tubular, radially expansible stent.
Devices for transluminal implantation of expanding stents or prostheses are previously known. Thus, U.S. Pat. No. 4,732,152 describes a device enabling transluminal implantation of self-expanding stents. The device described in said U.S. patent shows excellent performance in regard to enabling implantation of prostheses or stents in for example blood vessels or other ducts in living animal bodies. However, most implantation devices including that described in U.S. Pat. No. 4,732,152 suffer from the serious drawback of not enabling later extraction of an implanted prosthesis or stent. Such extraction of the implanted artifact will sometimes be necessary due to improper location or disturbances created by the presence of the stent.
In an attempt to solve the problem of extracting an implanted prosthesis or stent a device has been proposed, such as the one disclosed in published European patent application A1 0 364 420. Said device enabling transluminal implantation or extraction of radially self-expanding stents includes a central tube surrounded by an exterior tube axially displaceable relative to the central tube, and a plurality of axially extending spring members attached to the distal end of said central tube. These spring members are evenly distributed around the periphery of the central tube and capable of outwards springing action of their distal ends when retracting the exterior tube from the distal end of the central tube.
However, the device disclosed in said European patent application is associated with drawbacks in that the spring members engaging the stent from the outside in their expanded position are spaced apart so as not to cover the whole periphery of the stent causing deformation of the stent and also resulting in problems in the extraction procedure. This is particularly the case when operating with prostheses or stents of the type disclosed in U.S. Pat. No. 4,655,771. This particular type of prosthesis for use in transluminal implantation comprises a flexible tubular body composed of a braided arrangement of flexible thread elements involving free ends at the axial extremes of the prosthesis. In practical operation it has been found that using the device disclosed in European patent application A1 0 364 420 involves severe problems due to the fact that the spring members of said device in their expanded position cannot properly engage the end of the prosthesis in connection with the extraction procedure.